Scientists add letters to DNA's alphabet, raising hope and fear

Scientists reported Wednesday that they had taken a significant step toward altering the fundamental alphabet of life, creating for the first time an organism with DNA containing artificial genetic code.

The accomplishment might eventually lead to organisms that can make medicines or industrial products that cells with only the natural genetic code cannot. The scientists behind the work at the Scripps Research Institute have already formed a company to try to use the technique to develop new antibiotics, vaccines and other products, though a lot more work needs to be done before this is practical.

The work also gives some support to the concept that life can exist elsewhere in the universe using genetics different from those on Earth.

"This is the first time that you have had a living cell manage an alien genetic alphabet," said Steven A. Benner, a researcher in the field at the Foundation for Applied Molecular Evolution in Gainesville, who was not involved in the new work.

But the research, published online by the journal Nature, is bound to raise safety concerns and questions about whether humans are playing God. The new paper could intensify calls for greater regulation of the budding field known as synthetic biology, which involves the creation of biological systems intended for specific purposes.

"The arrival of this unprecedented 'alien' life form could in time have far-reaching ethical, legal and regulatory implications," Jim Thomas of the ETC Group, a Canadian advocacy organization, said in an email.

Despite the great diversity of life on Earth, all species, from simple bacteria to human beings, use the same genetic code. It consists of four chemical units in DNA, sometimes called nucleotides or bases, that are usually represented by the letters A, C, G and T. The sequence of these chemical units determines what proteins the cell makes. Those proteins in turn do most of the work in cells and are required for the structure, function and regulation of the body's tissues and organs.

The Scripps researchers chemically created two new nucleotides, which they called X and Y. In effect, the bacteria have a genetic code of six letters rather than four, perhaps allowing them to make novel proteins.

Floyd E. Romesberg, a chemist at Scripps who led the work, said the technique was safe because the synthetic nucleotides were fed to the bacteria. Should the bacteria escape into the environment or enter someone's body, they would not be able to obtain the needed synthetic material and would either die or revert to using only natural DNA.

"This could never infect something," he said.

That is one reason the company he co-founded, Synthorx, is looking at using the technique to grow viruses or bacteria to be used as live vaccines. Once in the bloodstream, they would conceivably induce an immune response but not be able to reproduce.